A large scale service provider network, e.g., a Next Generation Network (NGN), typically consists of multiple regional access offices and server offices connected to a backbone network, e.g., via uplinks between pairs of provider edge (PE) and customer edge (CE) routers. NGN access offices can be deployed with session border controllers (S/BC) to provide secured access by user endpoint devices (UEs) from public accesses and PSTN media gateways (MGW) for connectivity with Time Division Multiplexing (TDM) based telephony networks. Server offices can be deployed with call servers such as Call Session Control Functions (CSCF), Home Subscriber System (HSS), various application servers, media gateway control functions (MGCF), etc.
Public networks provide connectivity from UE to the public interfaces of S/BC. An NGN operator's internal backbone network provides inter-connectivity for communications of all other network elements. Some part of these networks may have more limited transport resources than others. For example, the link bandwidth between PE and CE routers for access offices are crucial network resources for providing the NGN services to its subscribers.
NGN operators may size the link capacity based on the forecast subscriber number, bandwidth per call, various historical call volume parameters, and so on. However, some situations may cause dramatic increase of call volumes. For example, events such as natural disasters, e.g., earthquakes, can trigger massive calling events. Since it is not possible to deploy additional transport resources on the fly, the existing network resources can be overloaded, thereby compromising the service capability of the NGN network.
In addition to the massive calling events, a NGN is often designed with geographical redundancy. Subscribers who are normally homed at one access office or data center can be re-homed to another access office or data center if their home office is out of service. This event will also cause a dramatic increase of workload and traffic in the protection site.